You don't need to remove the rod, just check for it sucking air through the seal when the plenum has vacuum e.g. at idle.

sxbaz is talking about the pipework between the filter and the AFM. If it is too straight or too short, the AFM can end up reading air in both directions which messes with the ECU's head.

regarding breather set up...I'm assuming you have the left most pipe connected to the PCV and what the feck is that big old brass thing connecting the right most pipe to the elephant's trunk ?

If that is a one-way valve, that might be causing some of your troubles.

Since I've already taken the throttle body off, I might as well just remove the rod, unless you recommend otherwise? Hopefully I can get it all assembled again..

I've edited my answer to sxbaz's post, should have read his question properly before answering..

Oh, Is that pipe supposed to be connected?? That might explain a couple of issues I've been having..

That big old brass thingy is basically an adapter for the breather pipe going to the elephant's trunk, not a one-way valve. When I bought the Z32 AFM I got a new elephant trunk with it, but the breather pipe didn't fit into the trunk, so I had to make it fit!

sorry im a bit slow to get back to you but yes my elephants trunk didnt have enough bends/length in it really so it caused some irratic behaviour, im not sure ive totally fixed the issue but it did help.
Theres a thread on here called 'air straighteners' or something along those lines which i looked into and ended up trying it.

I dont think it will solve your issue but it maybe something to play around with if you run out of things to try

sorry im a bit slow to get back to you but yes my elephants trunk didnt have enough bends/length in it really so it caused some irratic behaviour, im not sure ive totally fixed the issue but it did help.
Theres a thread on here called 'air straighteners' or something along those lines which i looked into and ended up trying it.

I dont think it will solve your issue but it maybe something to play around with if you run out of things to try

Alrighty, got everything back together today, with a new seal on the TPS side of the throttle body.

Adjusted TPS, and took it for a drive. No pops/bangs when I start to accelerate after letting go of the throttle.. Took a small trip (20 mins ish), and only noticed a very faint pop one time. So it seems like the problem is 99,9% fixed.

Don't know exactly what fixed it, but as long as it's fixed I couldn't care less

Last things I've done are: Cleaned the throttle body and replaced the seal that had a small tear in it, and adjusted the TPS.

I'd guess that the TPS might not have been perfectly adjusted the last time I did it, don't think it is the seal, but I dunno!

Thanks a lot for all the help!

All that's left now is to try to get the AAC working as it's supposed to... Did a test today just for fun, supplied the AAC with 12V while engine was running. Idle went up a good amount, dropped down to 800 rpm again when I stopped giving it 12V. Maybe it's my ECU that is not working correctly?